1. Field of the Invention
This invention relates to a method of making a methyl methacrylate-lauryl methacrylate copolymer additive for use in hydraulic fluids and lubricating oils, and to a non-dispersant, shear stabilized, and wear inhibited Viscosity Index(VI)-improving concentrate composition for use in hydraulic fluids and lubricating oils. More particularly, this invention relates to a method of making a methyl methacrylate-lauryl methacrylate copolymer additive which has non-dispersant, shear stabilizing, VI-improving and wear inhibiting properties when employed in hydraulic fluids and lubricating oils, and to a non-dispersant, shear stabilized, and wear inhibited VI-improving concentrate composition comprising a base oil and an effective amount of a methyl methacrylate-lauryl methacrylate copolymer. The concentrate of the instant invention is particularly useful when added to hydraulic fluids and lubricating oils to impart VI-improvement, shear stability, and wear inhibiting properties to such fluids and oils.
2. Information Disclosure Statement
British Pat. GB 1,172,697 (Sargent et al.) discloses a two-stage process for the preparation of an oil-soluble graft copolymer useful as a VI-improver: in the first stage a monomer mixture of up to 50 wt. % readily polymerizable, monoethylenically unsaturated monomers (e.g. styrene, n-butyl methacrylate, methyl methacrylate and mixtures thereof) and at least 50 wt. % of one or more difficultly polymerizable, monoethylenically unsaturated monomers (e.g. lauryl methacrylate) is polymerized in the presence of an oil-soluble organic peroxide or hydroperoxide catalyst; in the second stage the polymerization is continued in the presence of an azobis(diisobutyronitrile) catalyst to provide the final oil-soluble graft copolymer product. The instant invention is distinguishable from GB 1,172,697 in that it discloses a two-stage polymerization reaction in which an organic peroxide or hydroperoxide catalyst must be employed, whereas the method of formulating the copolymer of the instant invention does not employ such a catalyst. Furthermore, the concentrate of the instant invention imparts shear stabilizing and wear inhibiting properties, whereas there is no discussion of such properties in GB 1,172,697.
U.S. Pat. No. 3,252,949 (Fields et al.) discloses the preparation and use of highly syndiotactic methacrylate polymers and copolymers (e.g. methyl methacrylate-lauryl methacrylate copolymers) as VI-improvers in mineral oils and functional fluids. The highly syndiotactic polymer-copolymers of U.S. Pat. No. 3,252,949 are formulated at 0.degree. C. using triethylboron as a catalyst, and thus are distinguishable from the copolymer of the instant invention, which is formulated at higher temperatures in the presence of an alkyl mercaptan and an azobis (isobutyronitrile) catalyst. In addition, U.S. Pat. No. 3,252,949 does not disclose any advantage of the highly syndiotactic polymers in terms of improved shear stability or wear protection, whereas the copolymer of the instant invention provides such improved shear stability and wear protection.
European Patent No. 225,598 (Derwent Abstract 87-164844/24) discloses highly shear stable and VI-improved lubricating oils comprising: (a) esters of methacrylic acid or other acids with straight chain unbranched C.sub.6 -C.sub.15 alcohols; (b) esters of methacrylic acid or other acids with straight chain, unbranched C.sub.16 -C.sub.30 alcohols; (c) esters of methacrylic or other acids with C.sub.8 -C.sub.40 branched alcohols; (d) esters of methacrylic acid or other acids with C.sub.1 -C.sub.7 alcohols; and (e) monomers copolymerizable by free radicals.
European Patent No. 164,807 (API Abstract 86-20502) discloses a multi-functional VI-improving additive for use in lubricating oils which is a graft copolymer with a molecular weight of 50,000-600,000 comprising: (a) a base copolymer of a C.sub.1 -C.sub.4 alkyl methacrylate and a C.sub.10 -C.sub.18 alkyl methacrylate; and (b) grafted monomers comprising at least one N-vinylimidazole, N-vinylpyrrolidone, vinyl pyridine of N, N- and dimethyl amino-ethyl methacrylate, and at least one compound of the formula EQU CH.sub.2 .dbd.C(CH.sub.3)CO(OCH.sub.2 CH.sub.2).sub.n NHR
where R is a C.sub.1 -C.sub.18 alkyl group. The additive is a VI-improver with dispersancy, detergency anti-wear, corrosion-inhibiting, and pour point-lowering characteristics.
European Patent No. 153,209 (API Abstract 85-22608) discloses a VI-improving and pour point-reducing additive for use in lubricating oils. The additive is a methacrylate terpolymer obtained by copolymerization of a mixture of: (a) C.sub.12 -C.sub.20 alkyl methacrylates; (b) C.sub.4 -C.sub.10 alkyl methacrylates; and (c) methyl methacrylate.
Polish Patent 124,235 (API Abstract 85-21855) discloses the preparation and use of a methacrylate-styrene copolymer as a pour point depressant and VI-improver in lubricating oils. The copolymer is obtained by reacting petrolatum, styrene, methyl methacrylate, a C.sub.10 -C.sub.22 alkyl methacrylates, and AIBN.
European Patent No. 151,467 (API Abstract 85-22491) discloses an aqueous functional fluid useful as a hydraulic or metal working fluid, including a lubricant or anti-corrosion liquid containing a copolymer additive prepared by reacting: (a) mono or dicarboxylic acids or their half esters with aliphatic C.sub.1 -C.sub.8 alcohols (e.g. methacrylic acid); (b) an unsaturated ester surfactant; (c) a methacrylic ester of an aliphatic C.sub.1 -C.sub.18 alcohol; (d) an ethylenically unsaturated comonomer; (e) compounds with multiple ethylenic unsaturation, (e.g. divinylbenzene); and (f) a regulator (e.g. dodecylmercaptan).
U.S. Pat. No. 4,493,777 (Snyder, Jr. et al.) discloses a substantially oil-free hydraulic or metal working fluid which exhibits good shear stability and wear protection due to the presence of a copolymer comprising the reaction product of: (a) at least one ethylenically unsaturated water-soluble monomer (e.g. methacrylic acid); (b) an ethylenically unsaturated water-insoluble monomer (e.g. lauryl or methyl methacrylate); and (c) a polyvinyl cross-linking monomer.
U.S. Pat. No. 4,469,611 (Snyder, Jr. et al.) discloses a substantially oil-free aqueous industrial fluid with superior lubricating and wear preventing characteristics comprising a water-soluble synthetic addition copolymer of: (a) an ethylenically unsaturated polyalkyleneoxy-containing monomer (preferably the acrylic/methacrylic acid ester of a nonionic surfactant alcohol); (b) an ethylenically unsaturated water-soluble monomer (e.g. methacrylic acid); and (c) an ethylenically unsaturated water-insoluble monomer (e.g. lauryl or methyl methacrylate).
U.S. Pat. No. 4,462,920 (Snyder, Jr. et al.) discloses a substantially oil-free aqueous industrial fluid with superior lubricating and wear preventing characteristics useful as hydraulic and metal working fluids comprising a water-soluble synthetic addition polymer of: (a) an ethylenically unsaturated polyvinyl cross-linking monomer; (b) an ethylenically unsaturated water-soluble monomer (e.g. methacrylic acid); (c) an ethylenically unsaturated water-insoluble monomer (e.g. lauryl or methyl methacrylate); and (d) an ethylenically unsaturated polyalkyleneoxy-containing monomer.